Our objective is to study the visual and motor contributions made by single units to the generation of primate smooth pursuit. In particular, investigations will be centered in the dorsolateral pontine nucleus (DLPN) where, in preliminary studies, we found units that have visual sensitivity and activity related to smooth pursuit eye movements. Eye movements will be monitored with the scleral search coil technique while recording from DLPN units in behaviorally trained, chronic monkeys. The response properties of DLPN units will be tested during smooth pursuit eye movements and during visual, optokinetic, and vestibular stimulation. The afferent and efferent connections of the relevant regions of the DLPN will be studied using electrophoretic injections of anatomical tracers (horseradish peroxidase and tritiated amino acids). These tracers will be placed in locations where smooth pursuit related units have been recorded. The anatomical findings will guide the future selection of new single unit recording sites. Electrical stimulation of the flocculus will be used to antidromically activate the various DLPN unit types to positively establish the connectivity of particular neurons with the cerebellum. Electrical stimulation of the middle temporal and posterior parietal cortex will be used to orthodromically activate smooth pursuit related DLPN units. This study will advance our understanding of the smooth pursuit system by providing insignt into the procession of information in the cortico-ponto-cerebellar component of smooth pursuit pathway. Our results should be of assistance in the diagnosis and treatment of a variety of disorders in which smooth pursuit is affected.